This invention relates to a method for producing 1,1,1,3,3-pentafluoropropane, which is useful as a foaming agent for foaming substances such as polyurethane, a refrigerant, and the like.
There are several conventional methods for producing 1,1,1,3,3-pentafluoropropane. For example, JP-A-Hei-6-256235 discloses a method for producing 1,1,1,3,3-pentafluoropropane from CF.sub.3 -CClX-CF.sub.2 Cl where X is hydrogen or chlorine, by catalytic hydrogenation. A preferable catalyst for this method is a common hydrogenation catalyst. U.S. Pat. No. 2,942,036 discloses a method of hydrogenating 1,2,2-trichloropentafluoropropane to produce 1,1,1,3,3-pentafluoropropane or 1,1,3,3,3-pentafluoro-1-propane or mixtures thereof. A catalyst for this method is palladium carried on activated carbon. These two methods mentioned hereinabove are superior in conversion and selectivity. However, these catalysts deteriorate considerably in these methods. Furthermore, it is necessary to prepare the raw material(s) of these methods in advance. Thus, these methods may not be suitable for the production of 1,1,1,3,3-pentafluoropropane in an industrial scale.
There is disclosed, in published English translation (pp. 1312-1317) of Izvestiya Akademii Nauk SSSR, Otdelenie Khimicheskikh Nauk, No. 8, pp. 1412-1418, August, 1960 (CA 55, 349f), a method for producing 1,1,1,3,3-pentafluoropropane by hydrogenating 1,1,3,3,3-pentafluoro-1-propene in the presence of Pd-Al.sub.2 O.sub.3. However, it is difficult to find the raw material of this method (i.e., 1,1,3,3,3-pentafluoro-1-propene) on the market.
There is another method for producing 1,1,1,3,3-pentafluoro-propane by fluorinating 1,1,1,3,3-pentachloropropane in a liquid phase in the presence of a catalyst (see WO96/01797). However, this method is relatively low in selectivity and yield.
Unlike 1,1,1,3,3-pentalfluoropropane mentioned hereinabove, there is known another compound, 1-chloro-3,3,3-trifluoropropene, which is useful as an intermediate of medicines, of agricultural chemicals, of functional materials, and of fluorohydrocarbons. This compound is obtained, for example, by the following first to fifth processes. In the first process, 1,1,1-trifluoropropane is chlorinated to obtain, 1,1,1-trifluoro-3,3-dichloropropane, and then this compound is dehydrochlorinated by an alcoholic basic compound to produce 1-chloro-3,3,3-trifluoropropene (see J. Am. Chem. Soc., 1942, 64, 1158). In the second process, hydrogen chloride is added to 3,3,3-trifluoropropyne to produce 1-chloro-3,3,3-trifluoropropene (see J. Chem. Soc., 1952, 3490). The second process is superior in conversion and selectivity. However, it is difficult to obtain the raw material of the second process (i.e., 3,3,3-trifluoropropyne) on the market. In the third process, 3-chloro-1,1,1-trifluoro,-3-iodopropane is dehydroiodinated by alcoholic potassium hydroxide to produce 1-chloro-3,3,3-trifluoropropene (see J. Chem. Soc., 1953, 1199). In the fourth process, 3-bromo-3-chloro-1,1,1-trifluoropropane is dehydrobrominated by an alcoholic potassium hydroxide (see R. N. Haszeldine, J. Chem. Soc., 15 1951, 2495). The third and fourth processes are superior in conversion and selectivity. However, according to these processes, there is needed more than stoichiometric amount of potassium hydroxide, and it is necessary to prepare the raw materials in advance. Thus, there are problems to apply these processes to an industrial scale production. In the fifth process, 1,3,3,3-tetrachloropropene is fluorinated by hydrogen fluoride in the presence of an antimony catalyst (see U.S. Pat. No. 2,787,646). In the fifth process, there are a problem that it is difficult to obtain the raw material of the reaction on the market, and another problem that the yield of 1-chloro-3,3,3-trifluoropropene is poor for the industrial scale production.